Commercially available folding knives are typically composed of a handle and a blade, wherein the blade is pivotally connected to the handle in order to be rotated about the pivot joint and thereby moved out of or stored into the handle. Such a folding knife can be easily and safely carried around for use because it is compact in size and has the blade stored in the handle when folded. Compared with knives whose blade cannot be put away, therefore, folding knives are far more convenient for divers, outdoor enthusiasts, soldiers, police officers, and so forth.
However, a conventional folding knife that has been used for a long time tends to have a buildup of grime in the handle, in addition to a worn, and hence blunt, blade. This is why a conventional folding knife must be disassembled after each relatively long period of use so that the grime can be removed from inside the handle and the blade taken out for grinding and polishing and then put back in place to restore the performance of the conventional folding knife. Besides, in order to ensure steady use by its users, a conventional folding knife is generally so designed that its blade is pivotally connected between two plates, and that the plates are subsequently put together and secured with screws or other elements to form a handle. While this conventional manufacturing method can keep the handle and the blade of a conventional folding knife from separating from each other due to the improper intervention of an external force during use, the securely fastened handle structure adds to the difficulty of disassembly of the conventional folding knife; in other words, the conventional folding knife cannot be easily, safely, or rapidly taken apart for cleaning or maintenance.
As a solution, improvements have been made to the conventional folding knife structure. For example, U.S. Pat. No. 9,586,328 B2, assigned to GB II Corporation of US, discloses an easily disassembled folding knife 800 as briefly described below with reference to FIG. 1 to FIG. 5. The folding knife 800 is composed of an upper handle portion 806, a lower handle portion 808, a blade 804, and a locking portion 840. The inner side of the lower handle portion 808 is protrudingly provided with a pivotally connecting post 834 adjacent to one end of the lower handle portion 808. The top side of the pivotally connecting post 834 is protrudingly provided with a first block 838. The junction between the first block 838 and the pivotally connecting post 834 is recessed to form a first engaging groove 836. The first block 838 is rectangular (or non-circular) and is protrudingly provided on the top side of the pivotally connecting post 834 in a tilted manner (see FIG. 3). The blade 804 is formed with a pivotally connecting hole 850 adjacent to one end of the blade 804. The pivotally connecting post 834 is configured to extend into the pivotally connecting hole 850 so that the blade 804 can rotate about an axis defined by the pivotally connecting post 834. The locking portion 840 has one end pivotally connected to the inner side of the lower handle portion 808 at a position adjacent to the opposite end of the lower handle portion 808. The top side of the locking portion 840 is protrudingly provided with a second block 846 adjacent to the aforesaid end of the locking portion 840. The second block 846 is also rectangular (or non-circular) and is configured to rotate along with the locking portion 840. The junction between the second block 846 and the locking portion 840 is also recessed to form a second engaging groove 844. The upper handle portion 806 is formed with a first opening 818 adjacent to one end of the upper handle portion 806 and a second opening 820 adjacent to the opposite end of the upper handle portion 806. The first opening 818 and the second opening 820 are rectangular (or non-circular) and match the first block 838 and the second block 846 respectively in configuration. The upper handle portion 806 is further protrudingly provided with two first engaging blocks 822 and two second engaging blocks 824. The first engaging blocks 822 correspond to two wall portions of the first opening 818 respectively and extend toward the first opening 818. The second engaging blocks 824 correspond to two wall portions of the second opening 820 respectively and extend toward the second opening 820.
With continued reference to FIG. 1 to FIG. 5, the folding knife 800 is assembled as follows. To begin with, the upper handle portion 806 must be placed at a specific angle with respect to the lower handle portion 808 such that the first opening 818 in the upper handle portion 806 corresponds to the first block 838 on the lower handle portion 808 (see FIG. 4). Next, the first block 838 is inserted through the first opening 818, and the locking portion 840 is rotated until the second block 846 thereon is oriented as shown in FIG. 4. Please note that the first engaging blocks 822 corresponding to the first opening 818 are now aligned with the first engaging groove 836 between the pivotally connecting post 834 and the first block 838, making it possible to rotate the upper handle portion 806. The upper handle portion 806 is subsequently rotated in order for the second opening 820 in the upper handle portion 806 to correspond to the second block 846 on the lower handle portion 808, and for the first block 838 to correspond no more to the first opening 818. After that, the second block 846 is inserted through the second opening 820 and thereby brings the second engaging blocks 824 corresponding to the second opening 820 into alignment with the second engaging groove 844 between the locking portion 840 and the second block 846. The locking portion 840 is then rotated again such that the second block 846, too, corresponds no more to the second opening 820. The first engaging blocks 822 and the second engaging blocks 824 are now engaged with the blocks 838, 846 respectively (see FIG. 1); as a result, the blade 804, the upper handle portion 806, and the lower handle portion 808 are put together as shown in FIG. 5 and FIG. 1. The blade 804 in this state can be rotated with respect to the upper handle portion 806 and the lower handle portion 808 about the axis defined by the pivotally connecting post 834 so as to be stored in a storage space formed between the upper handle portion 806 and the lower handle portion 808 (see FIG. 5) or be out of the storage space (see FIG. 1).
By the same token, referring to FIG. 2 to FIG. 4, disassembly of the folding knife 800 begins by rotating the locking portion 840 so that the second block 846 thereon corresponds to the second opening 820. Then, the upper handle portion 806 or the lower handle portion 808 is rotated until the first opening 818 corresponds to the first block 838, and only then can the folding knife 800 be dismantled by removing the upper handle portion 806, the lower handle portion 808, and the blade 804 in turn, with a view to cleaning or maintaining the aforesaid components or replacing the blade 804.
According to the above, the folding knife 800 (or a similar structure or mechanism) does allow rapid disassembly and reassembly by its users, but the following issues arise during use, as can be easily found by any user:
(1) While disassembling or reassembling the folding knife 800, a user must sequentially and repeatedly adjust the upper handle portion 806, the lower handle portion 808, and the locking portion 840 to their respective required positions with precision while gripping each of the aforesaid components with one or the other hand. Not only does the adjustment complicate the disassembly and reassembly of the folding knife 800 and therefore cause trouble to the user, but also the user's fingers or palms may be cut during the disassembly or reassembly process if the blade 804 is not gripped at an appropriate angle or by an appropriate portion.
(2) The blocks 838, 846 and the openings 818, 820 are not circular but have specific polygonal shapes. These structural features require precision machining during manufacture and hence incur high machining costs. In addition, one who tries to disassemble or reassemble the folding knife 800 must adjust the positions of the blocks 838, 846 and of the corresponding openings 818, 820 very carefully because the blocks 838, 846 cannot be inserted through the openings 818, 820 respectively unless the former are aligned with the latter. Undoubtedly, the time-consuming and difficult aligning process makes it difficult to disassemble and reassemble the folding knife 800.
(3) The thicknesses of the engaging blocks 822, 824 must be equal to or slightly smaller than the depths of the engaging grooves 836, 844 respectively in order for the engaging blocks 822, 824 to engage respectively with the engaging grooves 836, 844 and thereby bring about a locked state after the upper handle portion 806, the lower handle portion 808, and the locking portion 840 are rotated. It is consequently required that the manufacturing tolerances of the related components of the folding knife 800 be controlled within a very small range; otherwise, either the folding knife 800 may have problem being assembled, or the components may get loose or make noise after the folding knife 800 is forced into the assembled state, resulting in a high fraction defective corrigible only through precision machining. Such machining, however, leads to high production cost and may thus hinder the popularization of the folding knife 800 and similar products that feature easy disassembly and reassembly.
(4) While the folding knife 800 is being disassembled or reassembled, friction and compression between the edges of the engaging blocks 822, 824 and the edges of the engaging grooves 836, 844 are inevitable. After long-term use, therefore, the edges of the engaging blocks 822, 824 or of the engaging grooves 836, 844 are bound to be damaged or deformed. Once the damage or deformation aggravates over time, engagement between the engaging blocks 822, 824 and the engaging grooves 836, 844 may become impossible, and in that case, the folding knife 800 can no longer be disassembled and reassembled as designed.
(5) The folding knife 800 is so configured that only after the blocks 838, 846 and the corresponding openings 818, 820 are adjusted precisely to the correct corresponding positions can the blocks 838, 846 be inserted with ease through the openings 818, 820 respectively. If the folding knife 800 is of a relatively small size, the blocks 838, 846 and the corresponding openings 818, 820 will be, too, making it more difficult to align the blocks 838, 846 with the openings 818, 820 respectively, and the difficulty of, and danger associated with, disassembling and reassembling the folding knife 800 will increase significantly as a result.
As stated above, the conventional folding knives do have a large number of problems and drawbacks to be overcome. It is therefore an important issue for folding knife designers and manufacturers to design a novel folding knife whose components are simpler in structure and interconnection than before, and which consequently can be disassembled and reassembled faster and more easily and be safer and more convenient to use than its prior art counterparts.